Obamacare's most crucial deadline thus far is mere days away, sparking a mad dash as Americans seek health coverage for 2014 and put the system to its toughest test yet.

Consumers, insurance companies and federal and state authorities are scrambling ahead of Monday, the last day people in nearly all states have to choose a health insurance plan that is guaranteed to be in place on Jan. 1.

Even after revamps of HealthCare.gov, the federal portal to health coverage in 36 states, and improvements to some state-run insurance exchanges, technological problems and a tight time frame pose major challenges to people looking for insurance under the Affordable Care Act. Those include uninsured people and insured people whose policies expire Dec. 31, risking potentially costly gaps in their health benefits.

The coming days could strain the insurance exchanges, rendering a stark verdict on whether the Obama administration's weeks-long effort to fix HealthCare.gov was enough to handle an expected surge in people trying to get a health plan, while working through backlogs of pending applications. Failure would mean more than frustration for people trying to get covered, as those who fall through the cracks will be at risk of huge medical expenses if they become ill or injured in 2014.

The risks of failure were clearly evident Friday, when HealthCare.gov was inoperable, the Wall Street Journal reported.

After more than two months of frustrating struggles with HealthCare.gov and the federal exchange's telephone customer service system, Sharon Van Daele, a retiree in Tucson, Ariz., feels tantalizingly close to the finish line and intends to cross it by this weekend.

"I'm trying desperately to get this resolved before the 23rd," said Van Daele, 64. "It's been a long and difficult road. I started this on Oct. 4," she said. Van Daele's application was held up by a litany of problems that no one could help with, until she used the option made available this month to delete an application and start over, which she did last week.

"It was smooth -- very smooth. When I started in early October, it was horrible," said Van Daele, a cancer survivor. She's currently enrolled in a temporary Obamacare program for people who can't get private coverage, the Pre-Existing Condition Insurance Plan, which expires next month. Van Daele thinks she can get a comparable policy for about $250 a month, including the tax credits she will receive. "Now I'm seeing a light at the end of the tunnel," she said.

If she's able to complete the process in time, Van Daele will follow a rapidly growing number of people who've used the insurance exchanges to sign up for coverage in recent weeks.

Although nationwide enrollment in private coverage through the exchanges has a long way to go toward the 7 million people the Congressional Budget Office initially projected would enroll by the end of the sign-up period on March 31, the pace has picked up, and the share of enrollments threatened by faulty data delivered to insurance companies appears to be shrinking.

Through the end of November, nearly 365,000 people enrolled in private insurance via the exchanges, and more than 800,000 were deemed eligible for Medicaid, the Department of Health and Human Services announced last week. And Obama announced on Friday that half a million people have signed up in December alone, suggesting the pace of signups has accelerated.

In some state-run health insurance marketplaces, new figures could portend a big uptick by the end of the year. Enrollments into private insurance via Covered California sped up to more than 17,000 a day this week, and more than 50,000 people signed up from Monday to Wednesday. The jump brings Covered California's total enrollment above 200,000 since October, the exchange announced Thursday. New York, Kentucky, Connecticut and other states reported similar increases.

Ahead of the Dec. 23 deadline, the federal government and several state exchanges have taken steps to ease the messy transition into 2014, as has the insurance industry.

The federal government has increased staffing at its call centers to more than 12,000 people, and is reaching out directly to consumers who haven't completed their applications, senior administration officials told reporters Thursday. The insurance exchanges in California, Connecticut, Kentucky, New York and Washington state have taken similar measures, executives said during a conference call with reporters hosted by the advocacy group Families USA on Wednesday.

On Thursday, the administration revealed that individuals whose policies were canceled because they don't meet the Affordable Care Act's standards won't be subject to the law's individual mandate, and will be allowed to buy bare-bones catastrophic plans originally intended for people younger than 30 or those who demonstrated financial hardship. Senior administration officials estimated this option will apply to fewer than 500,000 people.

"If people are trying to get coverage by Jan. 1, have a policy that's running out and need that coverage, we are committed to getting them through the system," Health and Human Services Secretary Kathleen Sebelius said on HuffPost Live Thursday.

Insurance companies agreed this week to accept customers' first premium payments until Jan. 10 while still guaranteeing coverage on New Year's Day if people had enrolled on time. State-run exchanges in Maryland, Rhode Island, Oregon, Washington state and Minnesota extended their enrollment or payment dates even further.

Insurance companies like Health Care Service Corp., a Chicago-based company that operates Blue Cross Blue Shield plans in five states, and Bloomfield, Conn.-based Cigna also have geared up for the pre-holiday rush by bolstering their customer service and sales teams, according to spokespeople for the companies.

"We've staffed up for it. We know that there's a crunch," said Lisa Rubino, the executive at Long Beach, Calif.-based Molina Healthcare who oversees its exchange business in nine states. "There's a lot of folks looking to enroll," she said.

Concerns linger, however, about the federal exchanges' ability to provide insurers with accurate data about their new customers, which would jeopardize people's enrollments. And the situation in several states, such as Oregon, Maryland and Hawaii, is considerably shakier.

"We are aware of the fact that we are going to have to struggle with folks who went through the Cover Oregon process but somehow did not get to us in a timely manner," said Dawn Bonder, CEO of Health Republic Insurance of Oregon, based in Lake Oswego. "What we've been encouraging folks to do is, you can buy our plan directly through our website, and put your application into Cover Oregon immediately," she said.

In spite of indications that enrollment is rising, and stories of failures-turned-potential-successes like Sharon Van Daele, other consumers continue to struggle with the balky system.

Alan Wells of Bluff City, Tenn., was eager to get into the exchanges and tried to start the process in October. But the 61-year-old retired information technology professional is still stuck. "I kind of gave up," Wells said.

Wells is looking to replace the COBRA plan he's had since his involuntary retirement, which costs $340 a month. Wells' only income is Social Security, so he expects the law's tax credits would save him money. But he's been stymied at every turn, including his most recent attempt on Thursday. "I'm going to try it periodically," Wells said. "When it works, it will work."

This story has been updated with December's enrollment number.

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  • 1912

    Former President Theodore Roosevelt champions national health insurance as he unsuccessfully tries to ride his progressive Bull Moose Party back to the White House. (Photo by Topical Press Agency/Getty Images)

  • 1935

    President Franklin D. Roosevelt favors creating national health insurance amid the Great Depression but decides to push for Social Security first. (Photo by Keystone/Getty Images)

  • 1942

    Roosevelt establishes wage and price controls during World War II. Businesses can't attract workers with higher pay so they compete through added benefits, including health insurance, which grows into a workplace perk. (Photo by Hulton Archive/Getty Images)

  • 1945

    President Harry Truman calls on Congress to create a national insurance program for those who pay voluntary fees. The American Medical Association denounces the idea as "socialized medicine" and it goes nowhere. (Photo by Keystone/Getty Images)

  • 1960

    John F. Kennedy makes health care a major campaign issue but as president can't get a plan for the elderly through Congress. (Photo by Keystone/Getty Images)

  • 1965

    President Lyndon B. Johnson's legendary arm-twisting and a Congress dominated by his fellow Democrats lead to creation of two landmark government health programs: Medicare for the elderly and Medicaid for the poor. (AFP/AFP/Getty Images)

  • 1974

    President Richard Nixon wants to require employers to cover their workers and create federal subsidies to help everyone else buy private insurance. The Watergate scandal intervenes. (Photo by Keystone/Getty Images)

  • 1976

    President Jimmy Carter pushes a mandatory national health plan, but economic recession helps push it aside. (Photo by Central Press/Getty Images)

  • 1986

    President Ronald Reagan signs COBRA, a requirement that employers let former workers stay on the company health plan for 18 months after leaving a job, with workers bearing the cost. (MIKE SARGENT/AFP/Getty Images)

  • 1988

    Congress expands Medicare by adding a prescription drug benefit and catastrophic care coverage. It doesn't last long. Barraged by protests from older Americans upset about paying a tax to finance the additional coverage, Congress repeals the law the next year. (TIM SLOAN/AFP/Getty Images)

  • 1993

    President Bill Clinton puts first lady Hillary Rodham Clinton in charge of developing what becomes a 1,300-page plan for universal coverage. It requires businesses to cover their workers and mandates that everyone have health insurance. The plan meets Republican opposition, divides Democrats and comes under a firestorm of lobbying from businesses and the health care industry. It dies in the Senate. (PAUL J. RICHARDS/AFP/Getty Images)

  • 1997

    Clinton signs bipartisan legislation creating a state-federal program to provide coverage for millions of children in families of modest means whose incomes are too high to qualify for Medicaid. (JAMAL A. WILSON/AFP/Getty Images)

  • 2003

    President George W. Bush persuades Congress to add prescription drug coverage to Medicare in a major expansion of the program for older people. (STEPHEN JAFFE/AFP/Getty Images)

  • 2008

    Hillary Rodham Clinton promotes a sweeping health care plan in her bid for the Democratic presidential nomination. She loses to Obama, who has a less comprehensive plan. (PAUL RICHARDS/AFP/Getty Images)

  • 2009

    President Barack Obama and the Democratic-controlled Congress spend an intense year ironing out legislation to require most companies to cover their workers; mandate that everyone have coverage or pay a fine; require insurance companies to accept all comers, regardless of any pre-existing conditions; and assist people who can't afford insurance. (Alex Wong/Getty Images)

  • 2010

    With no Republican support, Congress passes the measure, designed to extend health care coverage to more than 30 million uninsured people. Republican opponents scorned the law as "Obamacare." (Mark Wilson/Getty Images)

  • 2012

    On a campaign tour in the Midwest, Obama himself embraces the term "Obamacare" and says the law shows "I do care." (BRENDAN SMIALOWSKI/AFP/Getty Images)